In biological and chemical assay processes and systems which operate with tubes containing samples of biological or chemical material it is important that the contents of the tubes remain isolated from the atmosphere in the lab and during storage so that the contents do not evaporate or become contaminated with foreign bodies. Therefore, it is common practice to seal tubes. This may be performed with a sealing membrane that, once punctured must be replaced, or it may be with a resealable membrane.
When the samples contained within the tubes are not subjected to frequent access, then a sealing membrane that is not resealable is sufficient. The sealing membrane may take the form of a foil, backed with an adhesive that may be heat or pressure sensitive. In order to apply such a sealing membrane to a tube, it is usual to bring the top of the tube into contact with a sealing membrane that has been treated with such an adhesive and then to apply heat or pressure, as applicable, to cause the adhesive to adhere to the top of the tube. In general it is often necessary to seal a large number of tubes at the same time and therefore the sealing membrane is applied to an array of tubes that are localised in a supporting storage rack. However, the racks in which the tubes are placed are designed to make the most economical use of space possible and therefore the upper rims at the tops of the tubes are often in close contact. Very accurate registration and positioning of the tubes is essential.
As technology advances it is possible to process smaller samples and therefore there is a growing demand for smaller tubes, exacerbating these problems. This has led to the situation where it is difficult to seal and separate a large number of very small tubes held in a rack.
In order to separate the sealed tubes in such close contact it has been found to be necessary to use an array of spring-loaded pins arranged beneath the storage rack for pressing a number of the tubes out of the rack into contact with a sealing membrane disposed above the plate, a hot platen relatively movable into contact with the sealing membrane to melt the sealing membrane to the tops of the tubes that have been raised from the rack by the pins, and a die plate with holes movable relatively past the tops of the newly sealed tubes in order to cut the sealing membrane around each tube and thus separate the sealed tubes from the remainder of the sealing membrane.
In order for there to be enough scrap sealing membrane left for it to remain intact with sufficient strength to be easily removed from the device without disintegration after the sealing and separation steps, the pins may be actuated to raise the tubes from the rack in a checkerboard pattern. This facilitates the use of the sealing membrane in the form of a continuous web that can be fed from a reel into the apparatus with the resultant scrap sealing membrane being wound onto a second reel.
Such automation of the sealing and separation of large arrays of small tubes requires relatively complex equipment, and in particular requires complex, moving, precision parts to be located both above and below a rack holding the array of tubes.
The use of a checkerboard pattern also results in a significant proportion of the continuous web of sealing membrane being wasted.
Accordingly, it is an object of the invention to provide a simplified apparatus and associated method for separating individual sealed tubes from an array. Another object of the invention is the reduction of waste sealing membrane.